The present invention relates, in general, to filament winding machines such as those used for the production of glass fiber products such as cylindrical casings, and more particularly relates to an improved guide structure for guiding filaments from a plurality of spools to form a multi-filament strand.
In automatic winding machines, it is known to provide a plurality of feed spools of filamentary material such as glass fibers which are gathered into a strand for use in laying up a fiberglass product such as a cylindrical casing or the like. In one such arrangement, the several spools are secured to a mounting plate which, in turn, is affixed to a support beam that is movable along three axes. The mounting plate carries a filament guide through which the filaments from each of the spools is directed. Normally, this guide is located centrally of all of the spools and gathers the filaments so that they can be drawn as a multi-filament strand through suitable eyes, or bushings, to a winding foot which is then controllable to guide the strand onto and around a suitable form. Motion of the mounting plate and of the winding foot is controlled to move the strand along a desired winding path to form the desired wound product.
One such filament guide in current use in such machines is of a simple annular shape and is supported generally horizontally below the mounting plate approximately in the center of the multiple feed spools. The individual filaments are drawn from the corresponding spools through the central aperture of the guide, and from the guide through a pulley or bushing beneath and to one side of the filament guide. Although such a guide serves to gather the filaments in the required manner, problems are encountered with this arrangement, since the filaments used in such a winding machine typically are impregnated with a bonding material, and as a result the surfaces of the filaments are rough and abrasive. Since the filaments may move at a relatively high speed through the filament guide, the rough filament surfaces cause excessive wear on the guide and produce an excessive and variable tension on the filaments as they are drawn off of the spools. Further, since the filaments are initially wound on the spools to form filament packages by the use of traversing feeders, which travel from one end of the spool to the other as the spool rotates, the filament which is drawn from the spool to the winding machine therefore also traverses from one end of the spool to the other repeatedly during the unwinding operation. This causes the filament to be continuously changing direction as it is fed to the guide and, in addition, the distance between the filament guide and the takeoff point on the spool is continuously changing. This causes the tension on the filaments to vary cyclically as it is fed, with each filament from its individual spool varying in a similar manner, but from different directions and at different rates, which depend upon the diameter of the spool, the tightness with which the filament was originally wound, and other variables. These changes in filament tension produce a strand which is not consistent in its characteristics, since each element in the strand maybe supplied to the product being wound at a different tension. Furthermore, the high tension caused by the abrasive material impregnated in the filaments can cause breakage of the individual filaments, and together these problems result in improper strand placement on the product being wound, and can, in addition, result in machine failure.